1. Field of the Invention.
The invention relates to the field of random-access memories, particularly those employing self-refreshing cells.
2. Prior Art
There is a continuing demand for random-access memories (RAMs) which consume minimal amounts of power, particularly during a standby mode. Such memories are especially necessary for battery operated systems or where battery backup is employed during power failures. For the most part, the demand for such low power memories has been met with complementary MOS RAMs. However, these CMOS RAMs are more costly to fabricate when compared to other MOS memories.
The low power memory of the present invention employs n-channel devices in its presently preferred embodiment rather than CMOS devices. During standby, the memory draws only 20 microamps flrom a 5-volt supply for a 4K memory.
The self-refreshing, capacitance storage memory cell used in the disclosed memory is generally described in U.S. Pat. No. 4,030,083. One problem with the memory cell described in this patent is that complete asynchronous operation between the refreshing signal and accessing signals cannot be obtained. This application describes an improvement on this cell which permits complete asynchronous operation.